Naphtha conversion process including hydrocracking and hydroreforming

ABSTRACT

LIGHT AND HEAVY NAPHTHA FRACTIONS ARE CONVERTED BY HYDROREFORMING AND HYDROCRACKING TO HIGH QUANTITY MOTOR FUEL IN HIGH YIELD. LIGHT NAPHTHA (180-400* F.) IS REFORMED CATALYTICALLY AND THE STABILIZED REFORMATE BLENDED WITH HEAVY NAPHTHA (400 TO 500* F.). THE MIXTURE IS   HYDROCRACKED IN THE PRESENCE OF PD-ZEOLITE CATALYST AT 650-800* F. HYDROCRACKATE (180-400* F.) IS FURTHER REFORMED CATALYTICALLY.

March 6, 1973 NAPHTHA Filed May 24, 1971 AND HYDROREFORMING R. L BENNER CONVERSION PaocEss lNCLUDING HYDROCRACKING FIGURE 1 2 Sheets-Sheet 1 k I2 9 H l4 ,5 A l4 /6 1' a 1 V ,ls

Q24 Ag? 20 INVENTOR ROBERT I. BENNER BYQLQJIL ATTORNEY March 6, 1973 R. l. BENNER 3,719,535

NAPHTHA couvmsxou PROCESS INCLUDING HYDROCRACKING AND HYDROREFORMING Filed May 24, 1971 2 Sheets-Sheet 2 FIGURE 2 EFFECT OF TEMPERATURE 0N HYDROCRACKING CHARGE STOCK 5L6 V HV. NAPHTHA LLl 48.4 v REFORMATE 0: o g I00 (c WELD) Q 3 o 60 & Wqp m g 50 T o 40 T o O 30 2 0 \Q 9 II o 6000 0 Z: 9 0 o D m 1 P o u ID 135000 1 HYDROCRACKER TEMPERATURE "F INVENTOR ROBERT l. BENNER BY MGM AT RNEY United States Patent 01 lice 3,719,586 Patented Mar. 6, 1973 3,719,586 NAPHTHA CONVERSION PROCESS INCLUDING HYDROCRACKING AND HYDROREFORMING Robert I. Benner, Upper Chichester, Pa., assignor to Sun Oil Company of Pennsylvania, Philadelphia, Pa. Filed May 24, 1971, Ser. No. 146,391 Int. Cl. C10g 37/10, 39/00 U.S. Cl. 208-66 6 Claims ABSTRACT OF THE DISCLOSURE Light and heavy naphtha fractions are converted by hydroreforming and hydrocracking to high quality motor fuel in high yield. Light naphtha (180-400 F.) is reformed catalytically and the stabilized reformate blended with heavy naphtha (400 to 500 F.). The mixture is hydrocracked in the presence of Pd-zeolite catalyst at 650800 F. Hydrocrackate (180-400 F.) is further reformed catalytically.

CROSS REFERENCES TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION One of the principal aims in the petroleum industry is to produce high octane gasoline components at maximum yields. This is particularly important in view of the recent efforts to reduce and eventually eliminate the use of anti-knock lead compounds in gasoline to avoid environmental pollution. Numerous processes produce high tane components, but many times at the expense of gasoline production. Such processes often yield motor fuel of the desired quality, but at high costs due to low yields. This invention provides an integrated sequence of processing steps which produces a maximum yield of high value gasoline. Processing results are sometimes expressed in the petroleum industry in terms of octanebarrels. This value is obtained by multiplying the yield of gasoline in barrels by the research octaine number. Jackman and Werling described the significance of octanebarrels in Hydrocarbon Processing, December 1961, vol. 40, No. 12, p. 101.

Hitherto, it has been known to convert naphtha feed stock into high octane motor fuel components by various combinations of petroleum refining processes such as pyrolytic cracking, hydrocracking and/or reforming.

US. Pat. 2,703,308, A. G. Oblad et al., Mar. 1, 1955, describes a process in which a topped crude oil charge is hydrocracked to produce a high octane light gasoline fraction and a naphtha fraction of relatively poor octane quality which is then reformed. The resulting reformate boiling below 400 F. is added to the high octane light gasoline fraction from the hydrocracking step. Reformate boiling above 400 F. is added to the feed to the hydrocracking zone. This process concerns the conversion only of a hydrocarbon charge stock which boils above the gasoline boiling range to gasoline of high octane rating. The present process also involves the conversion of material boiling in the gasoline range.

US. Pat. 2,987,466, I. F. Senger et al., June 6, 1961, discloses a process in which a naphtha, gas oil, or cycle oil from a cracking unit is first converted in a hydroisomerization-hydrocracking zone. The reaction product is stabilized and fractionated into an intermediate fraction and residue, the latter being recycled to the hydroisomerization-hydrocracking zone. The intermediate fraction is separated into aromatic and non-aromatic components by S0 extraction. The aromatics are used as high quality gasoline whereas the non-aromatic components are aromatized in a second conversion zone provided with a conventional reforming catalyst. The present invention does not involve any extraction step such as the S0 extraction step of the foregoing process.

SUMMARY OF THE INVENTION The present invention provides a multi-stage process for the concurrent conversion of both light and heavy naphtha fractions to high quality motor gasoline in high yield. The light and heavy naphtha feed materials boil mainly in the ranges of -400 F. and 400-500 F., respectively. The process comprises the following operational procedure:

(a) hydroreforming the light naphtha in the presence of a reforming catalyst in a first hydroforming step;

(b) recovering a C reformate;

(c) adding this reformate to the heavy naphtha and hydrocracking the mixture at 650800 F.,and 600-1000 p.s.i.g., more preferably in the range of 700-760 F., whereby low anti-knock value components of the reformate are cracked while the heavy naphtha is undergoing cracking;

(d) fractionating the hydrocrackate from step (c) to separate a fraction boiling mainly in the range of 180- 400 F.;

(e) and hydroforming the 180-400 P. fraction in a second and separate hydroforming step in the presence of a reforming catalyst.

Optionally, material boiling above 400 F. obtained in fractionating step (d) may be recycled to the hydrocracking step (c).

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, FIG. 1 is a schematic flow-sheet illustrating the process of the invention and FIG. 2 is a graphical representation of data from a hydrocracking operation.

DESCRIPTION Referring now to the drawing, a hydrocarbon feed containing light and heavy naphtha boiling mainly in the range of 180 to 500 F. is sent through line 1 into zone 4 and therein through a conventional hydrodesulfurization catalyst, e.g., cobalt molybdate and/or nickel molybdate on alumina, at desulfurizing conditions. The effluent is passed through line 3 to a fractionating zone 5, wherein it is separated into a light fraction removed through line 7, an intermediate fraction boiling mainly in the range 180 to 400 "F. and obtained through line 6, and a residue of heavy naphtha boiling mainly in the range 400-500 F. which passes from the bottom of the fractionator via line 8. The intermediate fraction in line 6 is admixed With hydrogen from line 12 and the mixture is preheated in heater 9 to a temperature sufiicient to effect reforming in zone 11. The reforming is carried out in a conventional manner employing any known or conventional reforming catalysts preferably disposed in a series of reactors with means for supplying heat between the reactors. Reformate removed through line 13 is stabilized in fractionating zone 14 to remove C and lighter material via line 15. Stabilized reformate withdrawn through line 16 is admixed with the heavy naphtha previously obtained through line 8. The mixture is then hydrocracked in hydrocracker 19 in the presence of hydro gen supplied through line 18 and any suitable hydrocracking catalyst. The hydrocrackate effluent passes through line 20 to distillation zone 21 from which C and lighter hydrocarbons are removed overhead via line 22. Also an intermediate fraction boiling in the range 50-180" F. is taken through line 24 and a hydrocrackate fraction boiling mainly in the range ISO-400 F. is obtained through line 25. Optionally, hydrocracker zone 19 can be operated under conditions which produce a residue boiling mainly in excess of 400 P. which is recycled by means of line 23 to hydrocracker zone 19 to extinction. The ISO-400 F. hydrocrackate fraction in line 25 is admixed with hydrogen from line 26 and the mixture is preheated in heater 27 and then aromatized in reformer zone 29. This reforming step likewise can be operated in a conventional manner using a conventional reforming catalyst. Reformate is sent from reformer zone 29 through line 30 to a gas separator 31 wherein C and lighter material are removed through line 32. A C high quality gasoline fraction is obtained through line 33.

The foregoing briefly describes the process of the present invention. In further elaboration thereon, light naphtha boiling mainly in the range 180400 F. is passed into a reforming zone provided with a reforming catalyst which can be any catalyst known in the art for reforming hydrocarbons. For example, the catalyst can be platinum on alumina which generally contains 0.1 to 2.0% platinum. Commercial reforming catalysts are extensively described in the literature. A catalyst containing platinum and alumina generally has a plurality of functions whereby such reactions as dehydrogenation, isomerization, cyclization and hydrocracking are promoted. In some cases a minor amount of halogen is incorporated in the catalyst to effect certain selectivity for hydrocarbon reactions. Ammonia may also be added to achieve certain effects. The chemistry of hydrocarbon reforming is generally known and one of the main reactions desired is the conversion of naphthenes to aromatics. The product derived from the first reformer 11 in this invention shows a large increase in aromaticity, as illustrated by the In the reforming stage and using light naphtha, condi tions can vary widely; thus, temperatures of 600-1000 F. are operable and the preferred range is 800-950 F. Within these temperature limits space velocities of 0.5-

10.0 volumes of naphtha per hour per volume of catalyst in the reactor zone can be employed. Space velocities of 0.25 to 5.0 provide the best results. Hydrogen should be introduced into the reforming zone at rates of about 0.2 to 20.0 moles of hydrogen per mole of hydrocarbon reactants. Reforming pressure can be maintained in the range of 50-1000 p.s.i.g.; more preferably, in the range of 100-750 p.s.i.g.

Referring again to the drawing, the heavy virgin naphtha from line 8 is admixed with stabilized reformate from line 16 in specific proportions in the range 1/ 9 to 9/1 by volume; more preferably, in the range 4/6 to 6/ 4. The mixture is fed to a hydrocracking zone 19 containing, for example, a commercial hydrocracking catalyst consisting of 0.5% palladium on Y-zeolite. The hydrocracking zone is maintained at a temperature of 65 0- 800 F.; more preferably 700-760 F. It will be evident from subsequent data that the temperature of the hydrocracking zone in this invention is an important variable for achieving maximum yield of high octane gasoline. The heavy naphtha-reformate feed is reacted in the hy drocracker zone at a pressure in the range 600-1000 p.s.i.g., preferably 650-750 p.s.i.g., in the presence of hydrogen. Operating conditions in the hydrocracker zone are selected within the ranges heretofore indicated so as to maximize isoparaffin formation without destroying the ring structure contained in the stabilized reformate or the virgin heavy naphtha while minimizing gas and coke formation. The final reforming step which takes place in reformer zone 29 converts the naphthenes, which either were formed in or passed through the hydrocracker zone 19, into aromatic hydrocarbons. Reformer 29 is operated under the same conditions as reformer 11.

EXAMPLES The following data illustrate the results that can be obtained by the sequence of processing steps in accordance with this invention.

Properties of desulfurized virgin naphtha and the two distillate fractions derived therefrom follow:

TABLE I Desull'urized virgin Reformer Heavy naphtha charge naphtha (line 3) (line 6) (line 8) 46. 0 50. 1 42. 9 332 308 367 338 312 374 363 325 396 436 365 443 474 392 478 10 15 20 16. 9 14. 8 15. 2 37. 1 33. 5 36. 8 45. 9 51. 3 48. 0 0. 1 4 F-l clear octane l 30 28. 8 30.1 Volume, bbls 57. 4: 42. 6 Octane, bbls 3, 000 1, 650 1, 280

1 Estimated.

Properties of stabilized reformate after the light naphtha has been reformed in zone 14 using a catalyst comprising 0.3% Pt on A1 0 at 950 F. and 450 p.s.i.g. in the presence of hydrogen are as follows:

The following is illustrative of the use of a blend of stabilized reformate and heavy naphtha as a feed stream to hydrocracking zone 19. A blend consisting of 48.4%

5 stabilized reformate and 51.6% heavy naphtha is hydrocracked under the following conditions:

In the foregoing hydrocracking, conditions used are such that no residue in line 23 is obtained. Instead, the fraction 180400 F. is maximized for subsequent reform- TABLE III ing to aromatics from the naphthenes therein. This re- Specific operating conditions for hydrocracking 5 forming, carried out in zone 29 to produce additional oc- (Z 19) tame-barrels, is represented by the following data:

Catalyst 0.5% Pd on Y-Zeolite. Temperature Variable. TABLE V Pressure, p.s.i.g. 700. Recycle Gas Rate, s.c.f./ b. 5000. 10 Reforming Hydrocrackate LHSV, v./hr./v. 2.0.

The catalyst employed in the foregoing operation comgatalyst: 7 prises essentially a crystalline alumino-silicate having a g86 pore size sufficient to absorb benzene and with a crystal- 5 i i linity of at least 5% or more preferably -100% and Hydrocrackate 180-400 (from 732 0.5% Pd in addition to 3.6% F. It has a surface area dmcrackmg of 704 square meters/ g. and a pore volume of 0.35 cc./ g.

The data shown in Table IV and illustrated graphically P operties f R formed Hydrocrackate in FIG. 2 are typical of the results obtained. These data illustrate the importance of hydrocracker operating tem- Stabilized Reformate perature to maximize octane-barrels. Good results are (line 33) realized at temperatures in the range of 650-800 F., Gravity 42.8 especially good results are obtained in the range of about Engler R: 700-760 F., more particularly at about 732 F. under 5 190 the conditions therein described. This is evidenced in FIG. 50 290 2 curve C wherein the yield of octane-barrels with respect 95 404 to operating temperature reaches a maximum at about Composition, volume percent: 732 F. Although motor fuels produced at temperatures in Aromatics 72 excess of about 732 F. have high anti-knock values, their Naphthenes 11 volumes are lessened due to gas and coke formation and Paraifins 17 an apparent destruction of ring structures which effects Olefins have, as a net result, a decrease in octane-barrels. Curve Volume, bbls. 49.8 A, FIG. 2, illustrates the decrease of C yield at tem- Research, octane, clear 94.0 peratures in excess of 732 F. due to gas and coke for- Octane-bbls, 4681 r nation. Curve B, FIG. 2, shows the effect of hydrocrack- 1 Based on 100 bbls charged to desulfuflzer ing temperature on yield of naphthene and aromatics measured in terms of volume percent of the hydrocracker I charge. An increase in temperature has the effect of caus- Thus Wlh he hoted, that refofmlhg of h h ing destruction of the ring structures on the other 40 crackate from hydrocracking at 732 F. increased the ochand, at temperatures l h about 73 F ism tame-barrels of high anti-knockvalue motor fuel by (4681 merization and aromatization are less pronounced and Total octahe'banels P P o my the resulting product is of low anti-knock value as shown hhlque q q of h g hydrocracklhg and reform in Table IV, while competing reactions such as gas and h operahohs 6,822 whlch the summation of h h' coke formation and destruction of ring Structures are line fractions derived from the hydrocrackate boiling in less apparent the range 180 F. (2141) and the reformed hydro- Curve C, FIG. 2, illustrates the decrease in octanecrackate hchhhg ih the hahge 1804000 (4681) m barrels at temperatures less than about 732 F. due largely cordahce h the foregolhg exahhlhe' to ineffective isomerization and aromatization. A comparison of results of my invention with one con- Referring to Table IV, the octanegbarrel value of hydro 50 yentional processing scheme illustrates the improvement cracker feed stock (line 17) is 5360. However, with an m octahe'harrels' hhhough humerohs conventlohal octane number of 57.6, it does not represent a useable Scheme? may be h compansoh typlchl motor fuel for a modern internal combustion engine. Processlhg seqhehce 15 wherein heavyfiaphthallme 15 Motor fuels having a clear research octane number of hydrocrackeh uhder the h fh condltlons.whh' 76 and leaded research Octane of about 91 or more are out first being blended with stabilized reformate in acgenerally preferred.

TABLE IV [Properties of hydrocracker feed and products] Hydroeracker products (05+) at various operating temperatures Char e blend:

51.6%}, heavy 690 F. 732 F. 771 F. na htha, 48.4

p reformat? 50180 F. ISO-400 F. 50180 F. Rio-400 F. 50-180 F. 180400 F.

Gravity API 43. 4 79. 4 45. 5 80. 6 45. 8 79. 9 40. 2

l a F 262 102 266 106 234 106 238 364 125 330 123 290 126 276 444 160 416 156 394 172 370 34. 4 8. 1 38. 0 6. g g 11: $1 g N hth n 20. 9 16. 1 18. 9 14. Pgr hffin: eg 43. 9 75. 8 43. 1 78. 6 37. 7 78. O 22. 2 O1 fin 1. 0 Volum: liarrels 93 12. 5 75. 8 24. 9 55. 3 31. 1 31. 6 Research octane, clear 57. 6 86. 0 60. 7 86.0 71. 1 86.0 90. 1 Octane-barrels 5, 360 1, 075 4, 601 2, 141 3, 932 2, 670 2, 847 Total (50-400 F.) octane-barrels 5,360 ,7 5,676 (6,110) 6,073 (6,540) 5,517 (5,940)

1 Based on bbls. charged to desulfurizer (line 1).

2 octane-barrels based on 100 barrels charged to hydrocracker for Figure 2, Curve 0.

cordance with my invention. rels by these two processes follows:

TABLE VI.

Comparison of two reforming-hydrooraeking processes octane-barrel production under identical operating conditions] A conventional process This invention Reforming Stage 1,

oetane-bbls Hydrocraekiug Stage II- Charge: hvy. naphtha Reforming Stage 1,

octane-bbls 3, 400 Hydroeraeking Stage II -Charge: blend a Data from Table IV. 4 Reforming of 180-400 F. fraction from preceding Stage II.

The foregoing comparative data illustrate the improvement in octane-barrels of (6822-6488:) 445 obtained by the process of this invention as compared with a conventional processing scheme.

I claim as my invention:

1. In a process wherein a hydrocarbon feed is fractionated to obtain light and heavy naphtha fractions boiling mainly in the ranges of 180400 F. and 400-500 F., respectively, the light naphtha is hydroformed in a first hydroforming step in the presence of a reforming catalyst and the heavy naphtha is hydrocracked in the presence of a hydrocracking catalyst, the improvement which comprises;

(a) recovering 05+ reformate from said first hydroforming step and admixing substantially all of same A comparison of octane-bar- 8 with said heavy naphtha prior to the hydrocracking step;

(b) hydrocracking the resulting mixture at a temperature in the range of of 650800 F. and pressure in the range of 6001000 p.s.i.g., whereby low antiknock value components of said reformate are cracked while said heavy naphtha is undergoing hydrocracking;

(c) separately fractionating the hydrocrackate from step (b) to separate a fraction boiling mainly in the range 180-400 F.;

(d) and hydroforming said fraction in a second and separate hydroforming step in the presence of a reforming catalyst.

2. A process according to claim 1 wherein said heavy naphtha fraction boiling in the range 400500 F. and C reformate from step (a) are blended in a volume ratio in the range of 1/9 to 9/1.

3. A process according to claim 2 wherein said ratio is in the range of 4/6 to 6/4.

4. A process according to claim 1 wherein the hydrocracking temperature is within the range 700-760 F.

5. A process according to claim 1 wherein the hydrocracking catalyst comprises a noble metal on a zeolitic support.

6. A process according to claim 5 wherein the catalyst comprises palladium on Y-zeolite.

References Cited UNITED STATES PATENTS 3,535,225 10/1970 Jaife 208- 2,768,126 10/1956 Haensel et al. 208-66 3,159,566 12/1964 Sprague 208-66 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 208-60, 93 

